This application claims the priority of Japanese Application Nos. Hei 10-303519 filed Oct. 26, 1998, Hei 10-330561 filed Nov. 20, 1998 and International Application No. PCT/JP99/05829 filed Oct. 22, 1999, the complete disclosure of which are hereby incorporated by reference.
The present invention relates to an underground water tank for reserving rainwater having fallen onto a roof or rooftop of a house or onto a ground surface. More particularly, the present invention relates to a wide area water collection type underground water tank adapted to collect and reserve rainwater infiltrating into a relatively wide area and filtered thereby.
It has been conventionally known to bury a water tank underground and to reserve rainwater in the water tank, so as to effectively utilize the rainwater. In such a water tank, rainwater having fallen onto a roof or rooftop of a house or onto a ground surface is reserved in the water tank by collecting and guiding the rainwater by an eaves trough or gutter into the water tank. Further, such a water tank is provided with draining means such as a pump at an aboveground position for drawing out the water reserved within the water tank, so that the water reserved within the water tank is drawn out therefrom for use.
In the aforementioned underground water tank, however, since rainwater is collected by an eaves trough or gutter, the collected water itself is contaminated with impurities such as dust and dirt, thereby problematically restricting the usage of the reserved water and causing contamination of the interior of the water tank such as by the dust and dirt. Particularly, the reserving tank buried underground problematically leads to difficulty in cleaning the once contaminated reserving tank and causes an increased burden of management of the reserving tank. Further, building a plurality of houses or factories on the ground surface under which the reserving tank has been buried will complicate: the provision of routes of an eaves trough or gutter for guiding rainwater to the water tank; and the collection of rainwater having fallen over a relatively wide area.
It is therefore a first object of the present invention to provide a wide area water collection type underground water tank capable of effectively collecting rainwater having fallen over a wide area and of reserving the collected rainwater.
It is a second object of the present invention to provide a wide area water collection type underground water tank capable of reserving relatively clean infiltrating/filtered rainwater, to thereby reduce the burden of management of the water tank itself.
It is a third object of the present invention to provide a wide area water collection type underground water tank capable of preventing an occurrence of a flood, by preventing the underground from being saturated by the rainwater infiltrating thereinto, even upon a relatively much amount of rainfall.
As shown in FIG. 1, the invention according to claim 1 is a wide area water collection type underground water tank comprising: a water tank 11 constituted to be capable of reserving water therein, the water tank 11 being buried underground and having draining means 14 capable of drawing out the water within the water tank 11 from the aboveground position; one or two or more intake pipe 21 having one end communicated with the interior of the water tank 11 from the side portion or upper portion of the water tank 11, and the other end opened into the underground around the water tank 11; a check valve 31 mounted to the intake pipe 21, the check valve 31 being constituted to: allow water to flow from the other end of the intake pipe 21 toward the one end of the intake pipe 21 when the water pressure at the other end side of the intake pipe 21 is equal to or higher than that at the one end side of the intake pipe 21; and inhibit water from flowing from the one end of the intake pipe 21 toward the other end of the intake pipe 21 when the water pressure at the other end side of the intake pipe 21 is lower than that at the one end side of the intake pipe 21; and a water impermeable sheet 19 buried underground and being upwardly and outwardly inclined from the side or bottom of the water tank 11; wherein the other end of the intake pipe 21 is arranged near and above the water impermeable sheet 19.
According to the invention of claim 1, rainwater having fallen onto the ground surface infiltrates into the underground. The rainwater infiltrated into the underground is purified by the natural filtering effect by the ground, and the buried water impermeable sheet 19 guides the infiltrated rainwater down to the water tank 11 by the inclination of the water impermeable sheet 19. The thus guided water flows from the other end of the intake pipe 21 arranged near and above the water impermeable sheet 19, toward the one end side of the intake pipe 21 to thereby flow into the water tank 11. The water pressure at the other end side of the intake pipe 21 is equal to or higher than that at the one end side of the intake pipe 21 when no water is reserved within the water tank 11, so that the check valve 31 allows water to flow from the other end of the intake pipe 21 to the one end of the intake pipe 21. In this way, rainwater having fallen over a relatively wide area is filtered by the ground, and then collected by the water impermeable sheet 19 and reserved in the water tank 11.
Water is inhibited from flowing from the one end of the intake pipe 21 to the other end of the intake pipe 21, when the water tank 11 is filled up with rainwater so that the water pressure at the other end side of the intake pipe 21 becomes lower than that at the one end side of the intake pipe 21. Thus, the rainwater once reserved within the water tank 11 never leaks out via intake pipe 21, so that the rainwater is effectively reserved within the water tank 11. The water within the water tank 11 is drawn out therefrom, as required, by the draining means 14.
As shown in FIG. 14, the invention of claim 2 is a wide area water collection type underground water tank comprising: a water tank 11 constituted to be capable of reserving water therein, the water tank 11 being buried underground and having draining means 14 capable of drawing out the water within the water tank 11 from the aboveground position; one or two or more intake pipe 21 having one end communicated with the interior of the water tank 11 from the side portion or upper portion of the water tank 11, and the other end opened into the underground around the water tank 11; a check valve 31 mounted to the intake pipe 21, the check valve 31 being constituted to: allow water to flow from the other end of the intake pipe 21 toward the one end of the intake pipe 21 when the water pressure at the other end side of the intake pipe 21 is equal to or higher than that at the one end side of the intake pipe 21; and inhibit water from flowing from the one end of the intake pipe 21 toward the other end of the intake pipe 21 when the water pressure at the other end side of the intake pipe 21 is lower than that at the one end side of the intake pipe 21; and forcible check valve opening means 70 for controlling the check valve 31 so as to allow water to flow from the one end of the intake pipe 21 toward the other end of the intake pipe 21 even when the water pressure at the other end side of the intake pipe 21 is lower than that at the one end side of the intake pipe 21.
According to the invention of claim 2, the water tank 11 reserves water having infiltrated into the underground upon rainfall. Further, the check valve 31 is controlled by the forcible check valve opening means 70, when the water pressure at the other end side of the intake pipe 21 becomes lower than that of the one end side of the intake pipe 21 since the water existing within the ground around the water tank 11 evaporates or infiltrates into the deeper underground upon subsequent fine weather. Controlling the check valve 31 allows water to flow from the one end of the intake pipe 21 toward the other end of the intake pipe 21, and the reserved water flows from the one end of the intake pipe 21 toward the other end of the intake pipe 21 and leaks out from the water through-holes 42a of the perforated pipe 42 into the ground around the water tank 11. In this way, there is again formed a space within the water tank 11 for reserving rainwater. Thus, by controlling the check valve 31, it becomes possible to constantly prepare a space capable of temporarily reserving a constant amount of rainwater infiltrating into the underground upon rainfall.
As shown in FIG. 14 and FIG. 15, the invention of claim 3 is based on the invention of claim 2 and is a wide area water collection type underground water tank, wherein the forcible check valve opening means 70 comprises: a float driving rod 71 provided vertically to reach a float 35 of the check valve 31 from the aboveground position; and an operation handle 72 arranged at the aboveground position and provided at the upper end of the float driving rod 71.
According to the invention of claim 3, it is possible to allow water to flow from the one end of the intake pipe 21 toward the other end of the intake pipe 21, by controlling the check valve 31 with a relatively simple operation only to vertically move the float driving rod 71 by rotating the operation handle 72.
As shown in FIG. 1 and FIG. 5, the invention of claim 4 is based on the invention of anyone of claims 1 through 3, and is a wide area water collection type underground water tank further comprising: a perforated pipe 42 buried underground and formed with a plurality of water through-holes 42a at the periphery of the perforated pipe 42, wherein the perforated pipe 42 includes: one end connected to the other end of the intake pipe 21; and the other end buried in the underground at a level higher than the other end of the intake pipe 21.
According to the invention of claim 4, rainwater having infiltrated to the vicinity of the perforated pipe 42 is guided into the perforated pipe 42 via water through-holes 42a, and the rainwater guided into the perforated pipe 42 is guided by the perforated pipe 42 to the other end of the intake pipe 21. The water tank 11 reserves rainwater having fallen over a relatively wide area and collected by the perforated pipe 42.
The invention of claim 5 is based on the invention of claim 4 and is a wide area water collection type underground water tank wherein a gravel stratum 43 is provided around the perforated pipe 42.
According to the invention of claim 5, the gravel stratum 43 prevents clogging of the water through-holes 42a of the perforated pipe 42 due to soil and sand.
The invention according to claim 6 is based on the invention of anyone of claims 1 through 5, and is a wide area water collection type underground water tank further comprising a mounting member 41 buried near the water tank 11, wherein the check valve 31 is fixed to the mounting member 41.
According to the invention of claim 6, the mounting of the check valve 31 having directivity can be assuredly conducted by fixing the check valve 31 to the mounting member 41, to thereby prevent an inclination of the check valve 31 upon burying the same.